Interrater reliability of needle electromyographic findings in lumbar radiculopathy

This study was performed to investigate the interrater reliability of needle electromyographic findings and electrodiagnostic impressions among expert electrodiagnosticians.

Twenty-nine electromyographic recordings were chosen for this study from a larger prospective, observational cohort of 89 consecutive subjects, who were referred for electrodiagnostic evaluation of the lower limbs in a hospital-based spine clinic. The parent study was designed to evaluate the utility of electrodiagnostic findings in predicting outcomes after epidural steroid injections in lumbar radiculopathy. An unmasked, American Board of Electrodiagnostic Medicine board-certified examiner with knowledge of the patient's history and physical examination performed all initial electrodiagnostic evaluations, including needle electromyographic examination of a standardized set of six limb muscles and lumbar paraspinals representing L3 through S1 myotomes. The insertional and spontaneous activities of all muscles were recorded as de-identified digital video files with only muscle names visible. Motor units were not analyzed. Two independent, American Board of Electrodiagnostic Medicine board-certified examiners, who were masked to the patient's name, history, physical examination, and the electrodiagnostic report, reviewed 29 study subjects' digital video files. They rated each muscle's insertional and spontaneous activity on a standardized scoring sheet. After the examination was scored, they also generated a diagnostic impression of no evidence, possible evidence, or clear evidence of lumbar radiculopathy. Interrater reliability between the unmasked examiner and the two independent, masked examiners was assessed by Cohen's kappa statistic for electromyographic scoring of the muscles examined and for diagnostic impression.

The interrater reliability was substantial (kappa >0.60) showing >60% agreement for the scoring of most of the muscles examined. The overall diagnostic impression showed outstanding interrater reliability (kappa >0.90) showing >90% agreement between the unmasked and masked examiners. There were no significant differences in the scoring between the two masked examiners.

Needle electromyographic assessment of lower-limb and lumbar paraspinal muscles in the electrodiagnostic evaluation of lumbar radiculopathy is objective and highly reliable when performed by well trained and qualified electromyographers. Masked validation can be performed in electromyographic-based research.